1. Field of the Invention
The present invention relates to supply plan control methods and computer-readable recording media which have recorded a supply plan control program for accepting an order placed by a plurality of orderers distributed over remote places, and particularly to a supply plan control method and a computer-readable recording medium which has recorded a supply plan control program for accepting an order placed by orderers located in different time zones.
2. Description of the Related Art
Both domestic and international business transactions have been increasing. A purchase order handling system is used to accept orders from customers in different countries. The purchase order handling system accepts an order for a product from a customer in a foreign country and performs allocation in accordance with the supplier's supply plan. Then, the purchase order handling system returns shipment information (offered delivery date and the like) to the ordering terminal in the country (for instance, refer to Japanese Application No. 2000-293595).
Inventory-and-supply control methods for accepting an order, performing allocation, and offering a delivery date perform management on an equality basis or on a customer-by-customer basis. When a customer places an order for a product, the equality-basis inventory-and-supply control method allocates the ordered quantity of the product to the customer from the common inventory, as the product to be supplied. The customer-by-customer basis inventory-and-supply control method has stock products reserved for individual customers in advance. When a customer places an order for a product, the product to be supplied to the customer is allocated from the stock product reserved for the customer.
If the purchase order handling system operates 24 hours a day and accepts an order placed by different countries at any time of day or night, any of the conventional inventory-and-supply control methods will have problems as described later. An optimum supply plan should be managed especially for international transactions in consideration of time-zone differences.
FIG. 17 is a view showing examples of product allocation by conventional inventory-and-supply control methods. The upper half of FIG. 17 shows product management on an equality basis, and the lower half shows product management on a customer-by-customer basis.
The figure shows orders placed for a product and the allocation of the product on May 1. According to product demand forecasts for May 1, 150 pieces are to be manufactured as the pieces to be sold on May 1, 50 pieces are to be sold to an American customer, and 100 pieces are to be sold to a German customer.
In the shown example, a 24-hour day starts at 8:00 in the morning. The supplier located in Japan receives a first order for 60 pieces from the American customer at 9:00 Japan Time (order number P0-01:0001). The supplier receives a second order for 70 pieces from the German customer at 17:00 Japan Time (order number P0-02:0001). A third order for 10 pieces comes from the American customer at 2:00 on the next day Japan Time (order number P0-03:0001). A fourth order for 20 pieces comes from the German customer at 5:00 Japan Time (order number P0-04:0001). The local time of the American customer is 17 hours behind the Japan Time, and the local time of the German customer is 8 hours behind the Japan Time.
Product management on an equality basis (upper half of FIG. 17) will be described first. When the first order (order number P0-01:0001) is received, 60 pieces are allocated to the American customer, and 90 (150−60) pieces remain in stock. When the second order (order number P0-02:0001) is received, 70 pieces are allocated to the German customer, and 20 (90-70) pieces remain in stock. When the third order (order number P0-03:0001) is received, 10 pieces are allocated to the American customer, and 10 (20−10) pieces remain in stock. When the fourth order (order number P0-04:0001) is received, the last 10 pieces in stock are allocated to the German customer. Nothing (10−10=0) remains in stock, and the German customer is short by 10 pieces.
The American customer has placed an order for 70 pieces in total, beyond a forecast of 50 pieces, and receives allocation of all the 70 pieces. The German customer has placed an order for 90 pieces in total, lower than a forecast of 100 pieces, and faces a supply shortage. Product management on an equality basis has the following problems:                Product allocation is performed in order in which orders are placed regardless of time-zone differences, causing inequality among countries due to the time-zone differences.        The time when the latest supply plan is incorporated into the inventory information can be outside the local business hours of a customer. If a customer places a large-volume order immediately after the supply plan of a day is incorporated into the inventory information and if the incorporation time is outside the local business hours of another customer, the customer cannot receive production allocation of the day. The disregard for the time-zone differences will cause this type of inequality.        
Product management on a customer-by-customer basis (lower half of FIG. 17) will be described next. When the product is managed on a customer-by-customer basis, stock products are reserved in accordance with the supply plan.
When the first order (order number P0-01:0001) is received, 50 pieces are reserved as stocks for the American customer, and all those 50 pieces are allocated to the American customer. Stocks reserved for the American customer becomes 0 (50−50), and the American customer is short by 10 pieces. When the second order (order number P0-02:0001) is received, 70 pieces are allocated to the German customer from the stocks reserved for the German customer, and 30 (100−70) pieces remain as stocks reserved for the German customer. When the third order (order number P0-03:0001) is received, nothing is allocated to the American customer because no stocks are reserved for the American customer, and the American customer is short by another 10 pieces. When the fourth order (order number P0-04:0001) is placed, 20 pieces are allocated to the German customer from the stocks reserved for the German customer, and 10 (30−20) pieces remain as stocks reserved for the German customer.
Although product allocation to the American customer is insufficient, excess inventory is carried for the German customer. This causes the following problems:                It is difficult to perform optimum management for all the customers. A supply plan is drawn up generally in accordance with demand forecasts, but it is difficult to estimate orders from general customers accurately. Accordingly, there is often a difference between the plan and the record. The difference will produce excess inventory or can cause the supplier to miss a business opportunity due to insufficient inventory.        